During certain interventional procedures that are directed at cardiac access, the patient is catheterized through an access point in a vein or artery. A catheter is routed to the heart or other region of the cardiovascular system through the access point, which may be created by a cutdown or a percutaneous access procedure. The catheter may be routed to a target location within the heart, cerebrovasculature, or other region of the cardiovascular system. In certain cases, it becomes necessary to create a hole in a cardiovascular structure so that catheters or devices can be routed through a wall so as to provide for placement on the other side of the wall. One such case is the need to punch a hole in the septum that divides the right atrium of the heart from the left atrium. Such atrial septal punctures are increasingly used to gain access to the left atrium by way of the central venous system and the right atrium. Access to the left atrium of the heart is often useful in therapeutic and diagnostic procedures such as, but not limited to, valve replacement, valve repair, electrophysiology mapping, cardiac ablation, atrial appendage plug placement, and the like.
The currently accepted procedure for left atrial access involves routing a needle called a Brockenbrough™ needle into the right atrium with the Brockenbrough needle pre-placed within a guiding catheter. The guiding catheter specifically preferred for use with a Brockenbrough needle is called a Mullins™ catheter. The Brockenbrough needle is a long punch formed from a stainless steel wire stylet that is surrounded by a stainless steel tube. The distal end of the stainless steel tube forms a relatively sharp circular punch capable of penetrating certain vascular structures such as the inter-atrial septum. Brockenbrough needle stylets are typically 0.013 to 0.014 inches in diameter while the stainless steel tube is generally between 0.045 and 0.050 inches in outside diameter. The Brockenbrough needle outside diameter is configured to slidingly fit within the central lumen of the Mullins catheter. The stainless steel tube is substantially straight along most of its length but is pre-bent into a curved or “J” shape at its distal end. A loop at the proximal end of the Brockenbrough stylet facilitates grasping of the stylet and performing manual advance or retraction. The current art considers the access to the right atrium from the femoral vein to be relatively straight so the current devices are straight except for the distal curve, which is shaped for the approach to the atrial septal wall.
The Brockenbrough needle, a relatively rigid structure, is operated by advancing the device, with its stylet wire advanced to blunt the sharp tip, within its guiding catheter through the inferior vena cava and into the superior vena cava. Under fluoroscopic guidance, the Brockenbrough needle, retracted inside the distal tip of the Mullins catheter, is withdrawn caudally into the right atrium until it falls or translates medially into the Fossa Ovalis. The force of the Brockenbrough needle/Mullins catheter assembly pushing against the relatively weak atrial septal wall causes the Fossa Ovalis to become tented toward the left atrium. The Brockenbrough needle, protected by the blunt distal tip of the Mullins catheter, is firmly held against the Fossa Ovalis of the atrial septum. Pressure monitoring and dye injection are carried out through the central lumen of the punch following removal of the stylet wire. The circular or hollow punch is next advanced distally to puncture a hole through the atrial septum. Erroneous placement of the punch can lead to penetration of adjacent structures such as the aorta, damage to which would cause potentially severe hemorrhage and potentially compromise the health of the patient. Thus, extreme care is exercised to verify location prior to the actual punching step. The Brockenbrough needle is next advanced through the atrial septum. The guide catheter, which includes a removable, tapered, distal dilator, having a central lumen for the Brockenbrough needle, is advanced over the Brockenbrough needle system and into the left atrium. The Brockenbrough needle is next removed from the Mullins guide catheter along with the central dilator or obturator.
A main disadvantage of this system is that the Brockenbrough needle system is pre-curved at its distal end and is relatively rigid. This pre-curving, rigidity, and necessary distal sharpness causes the Brockenbrough needle system to carve material from the interior wall of the otherwise straight guiding catheter when the Brockenbrough needle assembly is inserted therethrough. The material carved from the guide catheter could potentially be released into the cardiovascular system and generate emboli with any number of serious clinical sequelae. Should this embolic catheter material enter the left atrium it could flow into and block important arterial vasculature such as the coronary arteries or cerebrovasculature. Furthermore, advancing a pre-curved, rigid punch through the cardiovascular system is difficult and could potentially damage the vessel wall or any number of significant cardiovascular structures, during the advancement.
It would be desirable to have a Brockenbrough needle system that was initially straight and then became curved after being inserted into the guiding catheter. Such a straight Brockenbrough configuration would be advantageous during ex-vivo insertion as well as insertion after the guide catheter has already been placed into the cardiovascular system. During ex-vivo insertion, the debris can be flushed from the lumen of the guide catheter but complete removal is not assured and emboli can still be generated by the device. However, if the guide catheter was already inserted into the cardiovascular system, the debris could not be flushed out ahead of time and could easily flow toward or be released into the cardiovascular system with potentially catastrophic or fatal results. Furthermore, the needle or punch could be more easily advanced into the body lumen if it were not pre-curved.